Influences on the Simon Effect of Prior Practice with Spatially Incompatible Mappings: Transfer within and between Horizontal and Vertical Dimensions

Article excerpt

The Simon effect refers to the fact that for tasks in which stimulus location is irrelevant and a nonspatial attribute is relevant, responses are typically faster when stimulus and response locations correspond than when they do not. Two experiments examined the influence of prior practice with an incompatible relevant spatial mapping on the Simon effect as a function of the dimension (vertical or horizontal) along which the stimuli and responses varied in practice and transfer sessions. With 72 practice trials, the Simon effect in the transfer session was eliminated only when the spatial dimension was horizontal for both practice and transfer. With 600 practice trials, the Simon effect was eliminated for all combinations of practice and transfer dimensions, with noncorresponding responses showing an advantage when the dimension was horizontal for both practice and transfer. Within-dimension transfer effects for the horizontal dimension after a small amount of practice can be attributed to reactivation of specific stimulus-response associations defined for the practice task. However, the between-dimension transfer effects evident after a larger amount of practice cannot be explained in this manner and suggest that the subjects acquired a general procedure of responding opposite to the stimulus location.

Stimulus-response compatibility (SRC) refers to the fact that performance is better with certain mappings of stimuli to responses than with others (Proctor & Vu, 2006). When left and right stimulus locations are mapped to left and right keypresses, the mapping of a left stimulus to a left response and a right stimulus to a right response yields better performance than does the alternative mapping. Spatial compatibility effects also occur when stimulus location is irrelevant and the relevant information is conveyed by a nonspatial stimulus attribute (e.g., color or shape), a phenomenon known as the Simon effect (Lu & Proctor, 1995; Simon, 1990; Simon & Rudell, 1967). Similar effects occur in two-choice tasks when the stimuli and responses are arrayed vertically (Nicoletti & Umilta, 1985; Vu, Pellicano, & Proctor, 2005; Vu, Proctor, & Pick, 2000).

Accounts of SRC and Simon Effects

Accounts of spatial SRC effects, including SRC proper and the Simon effect, have focused mainly on spatial coding, because compatibility effects depend on the relative positions of the stimuli and the responses (e.g., Nicoletti, Anzola, Luppino, Rizzolatti, & Umiltà, 1982; Roswarski & Proctor, 2000). All models include an intentional translation process that influences the speed of response selection for SRC proper (e.g., Duncan, 1977; Proctor & Reeve, 1985, 1986). Duncan proposed that SRC effects occur because S-R translation is accomplished by way of an identity rule (respond at the location that is the same as that of the stimulus) when the mapping is spatially compatible but by a less efficient respond-opposite rule (respond at the location that is opposite that of the stimulus) when it is incompatible. Although all models of SRC effects include a translational component, most recent models attribute SRC effects, in part, to a second process: direct (or automatic) activation of the corresponding response (e.g., Hommel, 1997; Kornblum, Hasbroucq, & Osman, 1990).

According to two-process models of compatibility effects, the corresponding response is activated regardless of whether stimulus location is relevant or irrelevant. For SRC proper, this activation is often assumed to facilitate responding when the mapping is compatible but to interfere when it is incompatible. For the Simon effect, responding is faster when the response assigned to the relevant stimulus attribute is the same as that activated by the stimulus position but slower when it is not, due to conflict between activated and assigned response codes. The Simon effect is typically attributed to automatic activation alone, whereas differences in translation efficiencies of the type mentioned above are presumed to contribute as well to the effect of SRC proper (e. …